Recently returned from London Heathrow on QF010. The evening in London was cool overcast and drizzling with rain. Traffic on the way to the airport was chaotic as is to be expected in a major city such as London. We returned our hire car to Budget on the North perimeter road, took the bus, checked in and spent some time in the BA Lounge. As the time for departure neared we made our way to the gate, went through security and sat, along with all the other passengers for our flight. Erveryone was a little uncomfortable as there were insufficent seats, departure was in the evening so I suppose most were a little weary and ready to board and settle in for the flight. Boarding time passed and then there was the announcement, our boarding would be delayed by 30 minutes due to the LATE ARRIVAL OF THE CREW, WHO HAD BEEN DELAYED BY TRAFFIC ON THEIR WAY TO THE AIRPORT. I am sympathetic to the crew, London traffic is hell but if all the passengers can manage to check in on time and wait around for three hours before the flight, surely the crew can factor bad traffic into their arrival time at the airport ?